Buggy code:
public class HTTPSampler2 extends HTTPSamplerBase { private static final Logger log = LoggingManager . getLoggerForClass ( ) ; static final String PROXY_HOST = System . getProperty ( "http.proxyHost" , "" ) ; private static final String NONPROXY_HOSTS = System . getProperty ( "http.nonProxyHosts" , "" ) ; static final int PROXY_PORT = Integer . parseInt ( System . getProperty ( "http.proxyPort" , "0" ) ) ; private static final boolean PROXY_DEFINED = ( ( HTTPSampler2 . PROXY_HOST . length ( ) ) > 0 ) && ( ( HTTPSampler2 . PROXY_PORT ) > 0 ) ; static final String PROXY_USER = JMeterUtils . getPropDefault ( HTTP_PROXY_USER , "" ) ; static final String PROXY_PASS = JMeterUtils . getPropDefault ( HTTP_PROXY_PASS , "" ) ; private static final String PROXY_DOMAIN = JMeterUtils . getPropDefault ( "http.proxyDomain" , "" ) ; static InetAddress localAddress = null ; private static final String localHost ; static final ThreadLocal httpClients = new ThreadLocal ( ) ; private static Set nonProxyHostFull = new HashSet ( ) ; private static List nonProxyHostSuffix = new ArrayList ( ) ; private static final int nonProxyHostSuffixSize ; static boolean isNonProxy ( String host ) { } private static boolean isPartialMatch ( String host ) { } private static void setDefaultParams ( ) { } public HTTPSampler2 ( ) { } private void sendPostData ( PostMethod post ) throws IOException { } HttpClient setupConnection ( URL u , HttpMethodBase httpMethod , HTTPSampleResult res ) throws IOException { } protected String getResponseHeaders ( HttpMethod method ) { } String setConnectionCookie ( HttpMethod method , URL u , CookieManager cookieManager ) { } String setConnectionHeaders ( HttpMethod method , URL u , HeaderManager headerManager ) { } void setConnectionAuthorization ( HttpClient client , URL u , AuthManager authManager ) { } protected HTTPSampleResult sample ( URL url , String method , boolean areFollowingRedirect , int frameDepth ) { String urlStr = url . toString ( ) ; HTTPSampler2 . log . debug ( ( "Start<seq2seq4repair_space>:<seq2seq4repair_space>sample" + urlStr ) ) ; HTTPSampler2 . log . debug ( ( "method" + method ) ) ; HttpMethodBase httpMethod = null ; if ( method . equals ( POST ) ) { httpMethod = new PostMethod ( urlStr ) ; } else if ( method . equals ( PUT ) ) { httpMethod = new PutMethod ( urlStr ) ; } else if ( method . equals ( HEAD ) ) { httpMethod = new HeadMethod ( urlStr ) ; } else if ( method . equals ( TRACE ) ) { httpMethod = new TraceMethod ( urlStr ) ; } else if ( method . equals ( OPTIONS ) ) { httpMethod = new OptionsMethod ( urlStr ) ; } else if ( method . equals ( DELETE ) ) { httpMethod = new DeleteMethod ( urlStr ) ; } else if ( method . equals ( GET ) ) { httpMethod = new GetMethod ( urlStr ) ; } else { HTTPSampler2 . log . error ( ( "Unexpected<seq2seq4repair_space>method<seq2seq4repair_space>(converted<seq2seq4repair_space>to<seq2seq4repair_space>GET):<seq2seq4repair_space>" + method ) ) ; httpMethod = new GetMethod ( urlStr ) ; } HTTPSampleResult res = new HTTPSampleResult ( ) ; res . setMonitor ( isMonitor ( ) ) ; res . setSampleLabel ( urlStr ) ; res . setHTTPMethod ( method ) ; res . sampleStart ( ) ; HttpClient client = null ; InputStream instream = null ; try { client = setupConnection ( url , httpMethod , res ) ; if ( method . equals ( POST ) ) { res . setQueryString ( getQueryString ( ) ) ; sendPostData ( ( ( PostMethod ) ( httpMethod ) ) ) ; } else if ( method . equals ( PUT ) ) { setPutHeaders ( ( ( PutMethod ) ( httpMethod ) ) ) ; } int statusCode = client . executeMethod ( httpMethod ) ; instream = httpMethod . getResponseBodyAsStream ( ) ; if ( instream != null ) { <START_BUG> Header responseHeader = httpMethod . getResponseHeader ( TRANSFER_ENCODING ) ; <END_BUG> if ( ( responseHeader != null ) && ( ENCODING_GZIP . equals ( responseHeader . getValue ( ) ) ) ) { instream = new GZIPInputStream ( instream ) ; } ByteArrayOutputStream outstream = new ByteArrayOutputStream ( ( 4 * 1024 ) ) ; byte [ ] buffer = new byte [ 4096 ] ; int len ; boolean first = true ; while ( ( len = instream . read ( buffer ) ) > 0 ) { if ( first ) { res . latencyEnd ( ) ; first = false ; } outstream . write ( buffer , 0 , len ) ; } res . setResponseData ( outstream . toByteArray ( ) ) ; outstream . close ( ) ; } res . sampleEnd ( ) ; res . setSampleLabel ( httpMethod . getURI ( ) . toString ( ) ) ; res . setResponseCode ( Integer . toString ( statusCode ) ) ; res . setSuccessful ( isSuccessCode ( statusCode ) ) ; res . setResponseMessage ( httpMethod . getStatusText ( ) ) ; String ct = null ; Header h = httpMethod . getResponseHeader ( HEADER_CONTENT_TYPE ) ; if ( h != null ) { ct = h . getValue ( ) ; res . setContentType ( ct ) ; res . setEncodingAndType ( ct ) ; } res . setResponseHeaders ( getResponseHeaders ( httpMethod ) ) ; if ( res . isRedirect ( ) ) { res . setRedirectLocation ( httpMethod . getResponseHeader ( HEADER_LOCATION ) . getValue ( ) ) ; } if ( getAutoRedirects ( ) ) { res . setURL ( new URL ( httpMethod . getURI ( ) . toString ( ) ) ) ; } saveConnectionCookies ( httpMethod , res . getURL ( ) , getCookieManager ( ) ) ; res = resultProcessing ( areFollowingRedirect , frameDepth , res ) ; HTTPSampler2 . log . debug ( "End<seq2seq4repair_space>:<seq2seq4repair_space>sample" ) ;

Fix:
Header responseHeader = httpMethod . getResponseHeader ( HEADER_CONTENT_ENCODING ) ;